Fans are used in a large variety of applications and operating conditions. For example, fans can be used for ventilating contaminated air and exhaust of combustion gases. In these applications, small particles, such as soot, may accumulate on the fan impeller and gradually cause a decrease in the efficiency of the fan.
Contamination of the fan impeller can be seen as a cause for some fan system failures. The mass of the impeller increases as foreign particles get stuck on the fan impeller. Because of vibration or careless maintenance, part of the additional mass may fall off, causing unbalance in the fan impeller. If the unbalance is not detected and corrected early enough, a fan failure may occur because of the higher vibration. Such a failure may lead to production losses or even to hazards to personnel. Thus, it may be desirable to detect contamination build-ups.
Contamination build-ups in fan impellers are visually detected or, if the contamination causes imbalance in the impeller, by vibration measurements. However, these methods include additional instrumentation or visual and/or manual inspection of the fan. Thus, they increase the operating cost of the application comprising fan impellers.